This invention relates to incinerators and more particularly to method and apparatus for continuously incinerating waste material. The invention is particularly adapted, among other possible uses for incinerating sewage sludge, municipal, industrial or community garbage, trash or refuse, for example.
Many different types of incinerators have been employed for such use including, for example, the well known Herreshoff type furnace, which is a multiple hearth type furnace having a plurality of vertically spaced hearths. In such installations the waste material is introduced to the furnace at the top and moves dowanwardly in a generally serpentine fashion moving alternately inwardly and outwardly across the hearths and is discharged at the bottom. Problems have been encountered with such furnaces due to the fact that the middle hearths tended to overheat beyond the structural design limits of the furnace. Heretofore, in order to overcome this problem it was thought necessary to add more air or oxygen at the bottom of the furnace. Thus, such a system frequently operated with as much as 100% excess air added at the bottom of the furnace in order to cool the central portion thereof to workable limits. I have found that such excess air tends to entrain or carry with it deleterious matter into the exhaust gases from the furnace. The problem of preventing air pollution in our present environment has become critical and, hence, large and expensive scrubbers or other exhaust gas cleaning devices were required.
The present invention overcomes the aforementioned problems in a new and improved manner, as will become apparent as the description proceeds.